Gas blast circuit breaker and operating means therefor



Dec. 12, 1967 J. BARKER ETAL 3,3

GAS BLAST CIRCUIT BREAKER AND OPERATING MEANS THEREFOR Filed Nov. 5, 1964 5 Sheets-Sheet 1 FIG.20

Dec. 12, 1967 J. BARKER ETAL 3,358,105

GAS BLAST CIRCUIT BREAKER AND OPERATING MEANS THEREFOR Filed Nov. 5, 1964 5 Sheets-Sheet 2 Dec. 12,1967 J. BARKER ETAL 3,358,105

GAS BLAST CIRCUIT BREAKER AND OPERATING MEANS THEREFOR Filed Nov. 5, 1964 E 5 Sheets-Sheet Dec. 12, 1967 .1. BARKER ETAL 3,358,105

GAS BLAST CIRCUIT BREAKER AND OPERATING MEANS THEREFOR Filed Nov. 5, 1964 5 Sheets-Sheet 4 Dec. 12, 1967 J, BARKER ETAL GAS BLAST CIRCUIT BREAKER AND OPERATING MEANS THEREFOR Filed Nov. 5, 1964 5 Sheets-Sheet 5 United States Patent 3,358,105 GAS BLAST CIRCUIT BREAKER AND OPERATING MEANS THEREFUR John Barker, John Robert Birt, Ernest Housby, and Derek Michael German, Stafford, England, assignors to The English Electric Company Limited, London, England, a British company Filed Nov. 5, 1964, Ser. No. 409,073 Claims priority, application Great Britain, Nov. 16, 1963, 45,347/63 Claims. (Cl. 200-143) AESTRACT OF THE DISCLOSURE A gas blast circuit breaker has two pairs of main con tacts and two pairs of secondary contacts, the latter being connected in parallel with the main contacts through resistors. The contacts are operated by fluid pressure means. A valve which is mechanically linked to the main contacts prevents opening of the secondary contacts until the main contacts have been opened. A fluid pressure-operated delay valve ensures that the main contacts are closed before the secondary contacts are closed.

This invention relates to circuit breakers, and in particular relates to gas blast circuit breakers.

Reference is made to application Serial No. 97,186, filed March 21, 1961 (now U.S. Patent No. 3,163,737) by Gouek et a1. and assigned to the same assignee as the present application.

The present invention consists in a circuit breaker having first and second pairs of switch contacts, and first and second fluid-operated devices for opening and closing the first and second pairs of switch contacts, respectively, said first device being adapted to be operated by a fiuid-pres sure source and said second device being connected in circuit with a fluid-operated time delay device and being adapted to be connected between said fluid-pressure source and a fluid outlet, said time delay device being operable, in response to the creation of a pressure diiference in said first device for opening the first contacts, to create a pressure difference in said second device to open said second contacts but with a time delay to ensure that the first switch contacts have opened before the second switch contacts open.

In order that the invention can be fully understood one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 illustrates a schematic circuit diagram of a circuit breaker according to this invention;

FIGURES 2a and 2b together show a part-sectional side elevation of a schematic layout of a circuit breaker according to this invention in which the main and auxiliary (resistor) interruptors are closed;

FIGURES 2c and 2d together show a part-sectional side elevation similar to that shown in FIGURES 2a and 21) but in which the main and auxiliary (resistor) interruptors are open;

FIGURE 3a illustrates a part-sectional plan View of a preferred constructional layout of the auxiliary interruptors and a shuttle valve associated therewith; and

FIGURE 3b illustrates a section through lines A-A in FIGURE 3a.

Referring now to FIGURE 1 the circuit breaker comprises a pair of main interruptors 1, 1' connected in series with a power transmission line and, connected in parallel with corresponding ones of the main interruptors, a series connected auxiliary (resistor) interruptor 2, 2' and a resistor 3, 3. The circuit breaker is so arranged that opening of the main interrupter 1 causes the resistor interruptor 2 to open a short while afterwards. In this way the duty of the main intcrruptor is relieved since at the instant the main interruptor opens the current passes through the resistor 3 in series with the switch 2, the high rate of rise of the recovery voltage appearing across the main intcrruptor being damped by this resistor. Subsequently, the resistor interruptor 2 is opened, this interruptor being designed to be capable of safely interrupting the reduced value of current flowing through the resistor 3.

In the arrangement to be described both main interruptors 1 and 1 will be opened together and both resistor interruptors 2 and 2 will be opened together, but as will be understood that the invention is not limited to such a symmetrical arrangement and the interruptors 1 and 2 could conveniently be operated independently of the interruptors 1' and 2'.

Referring now to FIGURES 2a and 2b there is shown a part-sectional side elevation of the circuit breaker which is substantially symmetrical about the line X-X.

The circuit breaker comprises a central casing 4 partially housing the main interruptor 1, and the main interruptor 1 (not shown). Disposed about the main interruptor 1 is a porcelain insulator 5 which is disposed between the central casing 4 and a conductive end plate 6 to which is connected one of the power line terminals 7 and a terminal 8 for the resistor 3. A contact 9 extends from the end plate 6 into the space enclosed by the porcelain insulator 5 and is resiliently mounted for limited movement although, in accordance with the normal terminology employed in this art, it will be referred to hereinafter as a fixed contact. Co-operating with the fixed contact 9 is a movable contact 10 which is arranged to slide reciprocably along a cylinder 11 enclosed within an inner extension of the casing 4. This movable contact 10 is connected by means of a rod 12 to a piston 13 slidable Within a cylinder 14. The rod 12 has a pin 15 extending therefrom which engages in a slot in one end of a lever 16 which is rotatable about the axis of a shaft 17 secured thereto. The other end of the lever 16 is connected to a cap 18, which, upon the initial movement of the lever 16 is arranged to compress a spring 19 connected between this cap 18 and a pivotable member Zil secured to an upstanding lug on the casing 4.

The rod-lever-spring arrangement is such as to give a toggle action, the spring 19 urging the movable contact 10 to an open or a closed position after the initial compression of this spring to its top-centre position.

A passage 21 adjoins the lower portion of the central casing 4 and communicates with a space 22 enclosed between the porcelain insulator 5 and the contacts 9 and 10, the passage 21 being supplied with a high-pressure gas from a source, not shown. A space 23 within the cylinder 11 is in communication with the space 22 when the contacts 9, 1d are open but is not in communication with the space 22 when these contacts are closed, as shown.

An exhaust valve 24 is mounted within an upper portion 25 of the casing 4 and is urged into a closed position by a coil spring 26. In the open position of this valve exhaust ports 27, open to the atmosphere, communicate with the space 23. The interior of the portion 25 is in communication through a conduit 28 with the space 22 so that it is in communication with the high pressure source. The valve 24 has an annular flange 29 which is slidable within the portion 25 and the space below this lip which is enclosed by the lip itself and the portion 25 can be placed in communication either with the pressure source or with atmosphere, as will be described below.

Integral with the upper portion 25 of the central casing is a housing 30 from opposite sides of which extend further porcelain insulators 31, 31 which are terminated by end plates 32, 32', respectively. A terminal 33 is secured to the left-hand end plate for receiving the other end of the resistor 3.

Disposed within the spaces enclosed by the corresponding ones of the porcelain insulators 31, 31 are the resistor interruptors 2, 2. For convenience only one of these resistor interruptors, namely interruptor 2, will be described in detail. Thus the left-hand interrupter 2 comprises a fixed contact 34, and a movable contact 35 which is slidably mounted in part of the housing 30. The movable contact 34 carries a piston 36 at its end remote from the fixed contact which is reciprocably slidable along a cylinder 37 enclosed within a portion of the housing 30. The contact 35 is provided with an end boss 38 adjacent the piston 36 and has a pin 39 extending therefrom which engages in a slot in one end of a pivotally mounted lever 40. The other end of this lever 40 is connected to a spring 41, the boss-lever-spring arrangement acting as a toggle to urge the movable contact 35 to either of its extreme end positions subsequent to the initial compression of the spring 41 to its top-centre positions.

A shuttle valve 42 is mounted for reciprocable movement in a common cylinder 43 enclosed within an upper portion of the housing 30, and this valve is resiliently urged into one end position by a coil spring 44. The shuttle valve comprises four ring pistons 45, 46, 47 and 48, and the left-hand end ring piston 45, remote from the spring 44 is in communication with a high pressure conduit 49 which communicates with a space 50, enclosed between the insulator 31 and the movable contact 35, and, through a conduit 51 and the conduit 28, to the high pressure source. The conduit 49 is also in communication with the common cylinder 43 of the shuttle valve between the ring pistons 45 and 46 and through a further conduit 52 to the cylinder space 37' of the right-hand resistor internuptor. Similarly, the cylinder space 37 of the left-hand resistor interruptor is in communication through a like conduit 52 to the common cylinder 43 between the ring pistons 47 and 48. In addition, the conduit 52 is either in communication with, or isolated from (as shown), a port 53 in dependence on the position of the ring piston 47. The port 53 communicates with an upper space 54 which in turn communicates with the space 23 within the central casing 4. The space 54 is in communication with the space 55 enclosed within the movable contact 35 throughout the whole length of movement of this contact and in addition a conduit 56 is in communication with this space 54 and is connected to a close delay" valve 57.

This valve 57 comprises a housing 58 which encloses a cylinder space 59 in which slides a bell-shaped piston 60 spring biased upwardly by a coil spring 61 into one of its end positions. The lower end of the bell-shaped piston comprises an annular end ring 62 the upper side of which is in communication with the conduit 56 and the upper end comprises a cap having a filamentary bore 63 extending therethrough which lies in alignment with the orifice of a high pressure conduit 64.

The housing 58 also encloses a chamber 65 which is in communication with the conduit 56 and includes a valve 66 which is spring biassed by a coil spring 67 normally to seal a bore 68 extending from this chamber to the cylinder space 59. Conduits 69, 69 extend through opposite sides of the Wall of the housing 58 to be in communication with, or isolated from, each other and the conduit 64 in dependence on the position of the piston 60, conduit 69 communicating with the left-hand side of piston 36 and conduit 69' communicating with the righthand side of piston 36'.

Disposed within the wall of the central casing 4 is a rotary valve 70 having a shaft which is mechanically coupled to the shaft 17 of the lever 16. The valve 70 has a diametral bore 71 extending therethrough which is either aligned with, or isolated from, as shown, a conduit 72 which communicates with that end of the cylinder space 43 which is sealed by the ring piston 48 in the shuttle valve.

The operating mechanism comprises a vertical rod 73 which is biassed upwardly by a spring 74 in a cylinder 75 so as to move upwardly when an operating detent (not shown) is tripped. A lever 76 is pivoted about a fixed axis 77 and is connected at one end to the rod 73 and at its other end to the centre of a bell cranked lever 78. One end of the lever 78 is connected to an operating rod 79 and the other end is connected to a rod 80 which in turn is connected to that end of the lever 16 adjacent the cap 18.

The operating rod 79 has a valve member 81 adjacent one end thereof and a further valve member 82 adjacent the other end thereof. The valve members 81 and 82 comprise. valve spools 83, 84, respectively, which are normally spring biassed into engagement with the operating rod 79. In one position, as shown, the valve member 81 communicates a conduit 85 extending from the passage 21 with a conduit 86 which communicates with the left-hand side of the piston 13, and the valve member 82 communicates a conduit 87 extending from the underside of the annular flange 29 of the piston 24 with a port 88 which is vented to atmosphere. In its other position the valve member 81 communicates the conduit 86 with a port 89 vented to atmosphere, and the valve member 82 communicates the conduit 87 with a conduit 90 which in turn communicates with the passage 21.

The operation of the circuit breaker will now be described with reference to FIGURES 2a and 2b in which the main and resistor interruptors are closed, and FIG- URES 2c and 2d in which the main and resistor interruptors are open. Each of these figures show the static, and not the intervening, positions of the circuit breaker components.

Initially, as shown in FIGURES 2a and 2b the con tacts of the main interruptor 1 are closed so that a circuit is completed between the terminals of the circuit breaker connected to the power transmission line. The contacts of the resistor interruptor 2 are also closed and the exhaust valve 24 is closed as are the rotary valve 70 and the shuttle valve 42.

When the operating rod 73 is tripped it moves upwardly and the lever 76 carries down with it the bell crank lever 78 which moves the spool 84 downwardly so as to communicate the pressure source, through passage 21 and conduit 90, with the underside of the flange 29 on the exhaust valve 24. The exhaust valve therefore moves upwardly and vents the space 23 to atmosphere through the ports 27. The resultant fall in pressure in the space 23 results in the movable contact 18 of the main interruptor moving away from the fixed contact 9 under the influence of the pressure applied to the left-hand side of the piston 13 through the conduits 85, 86. Lever 16 consequently moves to the position shown in FIG- URES 2c and 2d and rotates its shaft 17 thus aligning the bore 71 in the rotary valve 70 with the conduit 72. Since conduit 72 is now vented to atmosphere the shuttle valve 42 is urged to its right-hand position under the influence of the high pressure in the conduit 49 acting on the lefthand end of the ring piston 45.

Cylinder spaces 37, 37 are therefore cut-off from the high pressure source by reason of the conduits 49 and 52 and 49' and 52 being isolated from one another and the conduits 52 and 52 being communicated With the space 54, which is now at low pressure, through the ports 53, 53, respectively. As a result of the space 54, and thus conduit 56, being exhausted to atmosphere the piston 69 of the close relay valve moves downwardly under pressure from the conduit 64, the gas compressed thereby being exhausted through the port 68 and the valve 66, the conduits 69, 69 thus being placed in communication with the high pressure conduit 64.

This results in high pressure being applied through the conduit 69 to the left-hand side of the piston 36 in the resistor interruptor which causes the movable contact 35 to move towards the right-hand position, as shown in FIGURES 2c and 2d to open the resistor interrupter contacts.

Upon the opening of the resistor interruptor contacts a gas blast passes from the high pressure space 50 to the low pressure space 54 through the interior space 55 of the movable contact thereby assisting in extinguishing any are which may be drawn between the fixed and movable contacts.

Meanwhile, the opening of the main contacts 9 and 10 causes the rod 80 to be drawn towards its left-hand position thereby turning the bell crank lever 78 so as to reset the rod 79 and permit the spool 84 in the valve member 82 to move upwardly under its spring pressure.

Conduit 37 is thus vented to atmosphere through the port 88. Exhaust valve 2 5 thereby closes under the action of its spring 26 and the space 23 rapidly attains a high pressure again from the high pressure source through the restricted opening in the movable contact 10.

Since the rotary valve remains in the open position, as shown in FIGURES 2c and 2d the pressure in condult 72 rises and the shuttle valve 42 is reset to its lefthand position under the action of spring 44, the pressures in conduits 72 and 49 being substantially equal. In addition, as the pressure differential between that on the upper side of the piston 60 in the close delay valve and the cylinder space 59 thereof is reduced by the high pressure gas passing through the filamentary bore 63 this piston 60 slowly rises under the influence of its spring 61 to isolate the conduits 69, 69 from the high pressure conduit 64.

The circuit breaker is now in the open circuit position as shown in FIGURES 2c and 2d.

A closing operation is performed by moving the operating rod 73 downwardly against the restoring action of the spring 74 which consequently moves the rod '79 upwardly and vents the conduits 64 and 86 to atmosphere through the port 89. Since the conduit 86 is exhausted to atmosphere the main interruptor contacts close under the influence of the high pressure in space 23 upon the piston 13. This causes the lever 16 to turn and reset the lever 89 and rotate its shaft 17 which in turn causes the rotary valve 70 toclose to the position shown in FIG- URES 2a and 2b. The piston 60 in the close delay valve then moves downwardly under the action of the high pressure gas in the conduit 56 exhausting the conduits 69, 69 to atmosphere through conduit 64. The relief of pressure in conduit 69 enables the piston 36 of the resistor interruptor to move into its left-hand position under the action of the high pressure in conduits 52 and 49 consequently causing the movable contact 35 to close against the fixed contact 34, the toggle lever 40 operating in a similar manner to that of the lever 16 associated with the main interruptor, that is, to urge the movable contact 35 into its extreme limiting position after the spring 41 has been fully compressed,

After the main interruptor contacts have closed, the piston 13 continues to move to the left against the spring bias of contact 9 and eventually reaches the position shown in FIGURES 2a and 2b, whereupon the spool 83 is permitted to move downwardly. Therefore, the valve 81 is reset whereby the conduit 64 is again at high pressure and the piston 59 in the close delay valve slowly rises as the pressure differential between the conduit 64 and the cylinder 59 is reduced, the pressure conduit 56 operating on only a small area of the piston 62.

The main and resistor interruptor contacts are therefore returned to their position shown in FIGURES 2a and 2b.

As mentioned above, the layout illustrated in FIG- URES 2a to 2d is purely diagrammatic for the purpose of assisting in the description of the operation of the circuit breaker.

A preferred form of layout is illustrated in FIGURES 3a and 3b from which it will be apparent that for conserving space the two resistor interruptors are arranged alongside one another for part of their length and the shuttle valve is in fact housed in a common casing below the plane containing the axes of the two resistor interruptors. In these latter figures the same reference numerals have been appended to those parts which correspond to those shown in FIGURES 2a to 2d.

We claim:

1. A circuit breaker comprising a housing having therein an inlet chamber for receiving fluid under pressure, and an outlet chamber, a wall of said outlet chamber having therein an outlet port,

an exhaust valve movable to open and close said outlet port, and a fluid-operated exhaust-valve actuator,

a first pair of switch contacts, one of said contacts being hollow and mounted for movement in said housing in a position between said inlet and outlet chambers,

a first fluid-actuated device having a first cylinder, and a first piston movable in said cylinder and connected to said one contact, said first cylinder having therein a first port in fluid flow communication with said outlet chamber, and a second port, said first piston lying between said first and second ports,

a control valve,

a first duct connected between said control valve and said inlet chamber,

a second duct connected between said control valve and said second port,

a second .pair of switch contacts, one of said contacts being hollow and mounted for movement in said housing in a position between said inlet and outlet chambers,

a second fluid-actuated device having a second cylinder, and a second piston movable in said cylinder and connected to said one contact of the second pair of switch contacts,

said second cylinder having therein a third port and a fourth port, said second piston lying between said third and fourth ports,

a fluid-operated time-delay device comprising a cylinder having an inlet port, an outlet port and a control port, and a piston movable in said cylinder to open and close a fluid path between the inlet and outlet ports in dependence upon fluid-pressure diiference between the inlet port and the control port, the piston having a normal position in which it closes said fluid path,

a third duct connected between the inlet port of said cylinder of the time-delay device and said control valve,

a fourth duct connected between the control port of said cylinder of the time-delay device and said outlet chamber,

a fifth duct connected between the outlet port of said cylinder of the time delay device and said third port,

a third fluid-actuated device comprising a third cylinder having in side walls thereof a fifth port in fluid flow communication with said inlet chamber, a sixth port in fluid flow communication with said outlet chamber, and seventh and eighth ports in fluid flow communication with said fourth port,

a spool valve movable in said third cylinder between a first position in which it defines a flow path between said fifth and seventh ports are a second position in which it defines a flow path between said sixth and eighth ports, and

ducting connecting said control valve to said exhaustvalve actuator, said control valve being operable to supply fluid to said exhaust-valve actuator to open said outlet port thereby to create a pressure difference across said first piston to open said first pair of switch contacts, and create a pressure difference across said second piston, to open said second pair of switch contacts, after a time delay determined by said time-delay device.

2. A circuit breaker according to claim 1, comprising a sixth duct connected between one end of said third cylinder and said inlet chamber and a seventh duct connected between the other end of said third cylinder and said outlet chamber,

a further valve connected in said seventh duct, and

means connecting said further valve for movement with said first piston, whereby movement of said first piston in a direction to open said first pair of switch contacts' opens said further valve to permit fluid flow to said spool valve to move said spool valve from its said first position into its said second position.

3. A circuit breaker according to claim 1, wherein said piston in the time-delay device has a fluidbleed bore extending therethrough, said time-delay device further comprising a spring for urging said piston into its said normal position.

4. A circuit breaker comprising a first pair of electrical contacts relatively movable between an open and a closed state,

a second pair of electrical contacts relatively movable between an open and a closed state,

a first fluid-actuated device connected to the first pair of contacts and responsive to fluid pressure in an associated fluid circuit for relatively moving the said first pair of contacts between their said states,

a second fluid-actuated device connected to the second pair of contacts and responsive to fluid pressure in an associated fluid circuit for relatively moving the second pair of contacts between their said states,

control valve means connected in series with the said fluid circuit associated with the second fluid-actuated device for controlling the fluid pressure therein, said control valve means being movable between an open and a closed position,

means connecting said control valve means to said first fluid-actuated device whereby said valve means is in said closed position when said first pair of contacts are in said closed state and is in said open position when said first pair of contacts are in said open state,

means for applying fluid pressure across the fluid circuit associated with first fluid-actuated device and for simultaneously applying fluid pressure across the fluid circuit associated with the second fluid-actuated device in series with said control valve means, said first fluid-actuated device relatively moving said first contacts into said open state and said control valve means into said open position in response to said fluid pressure in its associated said fluid circuit whereby to :admit said fluid pressure to the fluid circuit associated with the second fluid-actuated device, and said second fluid-actuated device relatively moving said second pair of contacts into said open state in response to fluid pressure in its associated said fluid circuit, and

means providing a high fluid pressure environment around at least the said first pair of contacts both when they are in the open state and when they are in the closed state including an exhaust chamber having an exhaust port, and means for closing the exhaust port while the contacts are in said open state to maintain said high pressure environment around the first pair of contacts while they continuously remain in their open state.

5. A circuit breaker according to claim 4, in which the said first and the said second fluid-actuated devices respectively comprise first and second piston-cylinder assemblies, each piston-cylinder assembly including a piston rod connected to the said piston thereof and one contact of the respective said pair of contacts being car ried by the piston rod of each piston-cylinder assembly, the said control valve means comprising a rotary valve connected to the said piston-rod of the said first pistoncylinder assembly for rotation as the piston-rod moves.

6. A circuit breaker according to claim 4, in which the said means providing a high-pressure environment around the said first pair of contacts comprises a high pressure chamber surrounding the said first pair of contacts, and means connecting the high pressure chamber to a source of high fluid pressure, at least one contact of the said first pair of contacts including a surface defining an aperture which is closed when the said contacts are in the said closed state and which is open when the said contacts are in the said open state, the circuit breaker including said exhaust chamber having a Wall a portion of which includes the said surface defining the said aperture, means for opening said exhaust port before the said first pair of contacts are moved into the said open state whereby to create a high pressure fluid blast through the said aperture when the said first pair of contacts are moved to the said open state.

7. A circuit breaker comprising a first pair of electrical contacts relatively movable between an open and a closed state,

a second pair of electrical contacts relatively movable between an open and a closed state,

a first fluid actuated device connected to the first pair of contacts and including first and second fluid circuits, said first fluid actuated device being responsive to fluid pressure in the said first circuit for relatively moving the first pair of contacts into the said open state and being responsive to fluid pres sure in the said second fluid circuit for relatively moving the said first pair of contacts into the said closed state,

a second fluid actuated device connected to the second pair of contacts and including third and fourth fluid circuits, the said second fluid-actuated device being responsive to fluid pressure in the said third fluid circuit for relatively moving the said second pair of contacts into the said open state and being responsive to fluid pressure in the said fourth fluid circuit for relatively moving the said second pair of contacts into the said closed state,

control means for applying fluid pressure to the said first and the said third fluid circuits whereby to move the said first pair of contacts and the said second pair of contacts into their respective said open states,

time-delay valve means connected in series With said fourth fluid circuit and having an open and a closed position, said time-delay means being ibia'ssed into said closed position,

means for applying fluid pressure across said second fluid circuit and across said fourth fluid circuit in series with said time-delay valve means whereby said first fluid actuated device relatively moves said first pair of contacts into said closed state in response to said fluid pressure in said second fluid circuit, and for simultaneously actuating said time delay valve means whereby said time delay valve means moves into said open position after a predetermined time delay to apply fluid pressure across said fourth fluid circuit to cause said second fluid actuated device to move said second contacts into said closed state, and means providing a high fluid pressure environment around at least said first pair of contacts both when they are in the open state and when they are in the closed state including an exhaust chamber having an exhaust port, and means for closing the exhaust port while the contacts are in said open state to maintain said high pressure environment around the first pair of contacts while they continuously remain in their open state.

8. A circuit breaker according to claim 7, in which said time-delay valve means comprises a piston-cylinder assembly, said cylinder defining a port communicating with said fourth fluid circuit and said piston-cylinder assembly including spring means biassing said piston into a position into which it closes and the said port to prevent application of fluid pressure to the said fourth fluid circuit, the said means for opening the time-delay valve means comprising means for applying fluid pressure to the said piston whereby to move the said piston away from said port against said spring biassing means, the said piston defining a through filamentary bore through which fluid leaks so as to control the speed of movement of said piston.

9. A circuit breaker comprising a first pair of electrical contacts relatively movable between an open and a closed state,

a second pair of electrical contacts relatively movable between an open and a closed state,

a first fluid-actuated device connected to the said first pair of contacts and including first and second fluid circuits, whereby fluid pressure in the said first fluid circuit relatively moves the said first contacts into the said open state and fluid pressure in the said second fluid circuit relatively moves said first contacts into the said closed state,

a second fluid-actuated device connected to the second pair of contacts and including third and fourth fluid circuits, whereby fluid pressure in the said third fluid circuit relatively moves the second pair of contacts into the said open state and fluid pressure in the said fourth fluid circuit relatively moves the second pair of contacts into the said closed state,

control valve means connected in series with said means for applying fluid pressure across said first fluid circuit and simultaneously apply fluid pressure across said third fluid circuit in series with said control valve means whereby, in response to said fluid pressure in the said first fluid circuit, said first fluid-actuated device relatively moves the said first pair of contacts into the said open state and relatively moves the said control valve means into the said open position to admit fluid pressure to the said third fluid circuit, and whereby, in response to said fluid pressure in said third fluid circuit, the said second fluid-actuated device relatively moves the said second pair of contacts into the said open state, time-delay valve means connected in series with the said fourth fluid circuit, the said time-delay valve means including a pressure responsive valve normally biassed into a closed position but movable into an open position after a predetermined time delay in response to a control fluid pressure,

means for applying fluid pressure across the said second fluid circuit and across the fourth fluid circuit in series with said time-delay valve means in said closed position, whereby said first fluid-actuated device moves said first pair of contacts into the said closed state, and for substantially simultaneously applying said control fluid pressure to said time-delay valve means to move said time-delay valve means into its said open position to apply said fluid pressure across the fourth fluid circuit whereby the said second fluid-actuated device moves said second pair of contacts into said closed state after said predetermined time delay, and means providing a high fluid pressure environment around at least the said first pair of contacts both when they are in the open state and when they are in the closed state including an exhaust chamber having an exhaust port, and means for closing the exhaust port while the contacts are in said open state to maintain said high pressure environment around the first pair of contacts while they continuously remain in their open state.

10. A gas-blast electric circuit-breaker comprising, in combination,

a main circuit interrupter,

a resistor connected electrically in parallel with said main circuit interrupter,

a resistor circuit interrupter in series with said resistor,

closed chamber means enclosing said main and resistor circuit interrupters,

a source of gas under pressure connected to said closed chamber means,

a first gas-actuated device connected to said main circuit interrupter to operate it,

a second gas-actuated device connected to said resistor circuit interrupter to operate it,

an exhaust valve operable independently of said interrupters,

first passage means connecting said exhaust valve to said first gas-actuated device,

a rotary valve connected to said first gas-actuated device to be moved into an open position in response to operation of the said main circuit interrupter,

second passage means connecting said exhaust valve to one side of said rotary valve,

a shuttle valve having an open and a closed position,

third passage means connecting the other side of said rotary valve to one side of said shuttle valve,

fourth passage means connecting the other side of said shuttle valve to said second gas-actuated device,

means for opening said exhaust valve whereby to actuate said first gas-actuated device to operate said main circuit interrupter and to move said rotary valve into said open position, opening of said rotary valve moving said shuttle valve into said open position whereby to actuate said second gas-actuated device to operate said resistor circuit interrupter, and

fifth and sixth passage means in said main circuit interrupter and said resistor circuit interrupter respectively, said fifth and sixth passage means being opened when said main circuit interrupter and said resistor circuit interrupter are operated whereby on opening of said interrupters a blast of said gas under pressure passes over said interrupters and through said exhaust valve.

References Cited UNITED STATES PATENTS 2,892,913 6/1959 Thommen 200148 2,977,446 3/1961 Baker 200148 3,163,737 12/1964 Gonek et al. 200148 3,214,547 10/1965 Telford et a1. 200-148 ROBERT S. MACON, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

P. E. CRAWFORD, Assistant Examiner. 

1. A CIRCUIT BREAKER COMPRISING A HOUSING HAVING THEREIN AN INLET CHAMBER FOR RECEIVING FLUID UNDER PRESSURE, AND AN OUTLET CHAMBER, A WALL OF SAID OUTLET CHAMBER HAVING THEREING AN OUTLET PORT, AN EXHAUST VALVE MOVABLE TO OPEN AND CLOSE SAID OUTLET PORT, AND A FLUID-OPERATED EXHAUST-VALVE ACTUATOR, A FIRST PAIR OF SWITCH CONTRACTS, ONE OF SAID CONTACTS BEING HOLLOW AND MOUNTED FOR MOVEMENT IN SAID HOUSING IN A POSITION BETWEEN SAID INLET AND OUTLET CHAMBERS, A FIRST FLUID-ACTUATED DEVICE HAVING A FIRST CYLINDER, AND A FIRST PISTON MOVABLE IN SAID CYLINDER AND CONNECTED TO SAID ONE CONTACT, SAID FIRST CYLINDER HAVING THEREIN A FIRST PORT IN FLUID FLOW COMMUNICATION WITH SAID OUTLER CHAMBER, AND A SECOND PORT, SAID FIRST PISTON LYING BETWEEN SAID FIRST AND SECOND PORTS, A CONTROL VALVE, A FIRST DUCT CONNECTED BETWEEN SAID CONTROL VALVE AND SAID INLET CHAMBER, A SECOND DUCT CONNECTED BETWEEN SAID CONTROL VALVE AND SAID SECOND PORT, A SECOND PAIR OF SWITCH CONTACTS, ONE OF SAID CONTACTS BEING HOLLOW AND MOUNTED FOR MOVEMENT IN SAID HOUSING IN A POSITION BETWEEN SAID INLET AND OUTLET CHAMBERS, A SECOND FLUID-ACTUATED DEVICE HAVING A SECOND CYLINDER, AND A SECOND PISTON MOVABLE IN SAID CYLINDER AND CONNECTED TO SAID ONE CONTACT OF THE SECOND PAIR OF SWITCH CONTACTS, SAID SECOND CYLINDER HAVING THEREIN A THIRD PORT AND A FOURTH PORT, SAID SECOND PISTON LYING BETWEEN SAID THIRD AND FOURTH PORTS, A FLUID-OPERATED TIME-DELAY DEVICE COMPRISING A CYLINDER HAVING AN INLET PORT, AN OUTLET PORT AND A CONTROL PORT, AND A PISTON MOVABLE IN SAID CYLINDER TO OPEN AND CLOSE A FLUID PATH BETWEEN THE INLET AND OUTLET PORTS INDEPENDENCE UPON FLUID-PRESSURE DIFFERENCE BETWEEN THE INLET PORT AND THE CONTROL PORT, THE PISTON HAVING A NORMAL POSITION IN WHICH IT CLOSES SAID FLUID PATH, A THIRD DUCT CONNECTED BETWEEN THE INLET PORT OF SAID CYLINDER OF THE TIME-DELAY DEVICE AND SAID CONTROL VALVE, A FOURTH DUCT CONNECTED BETWEEN THE CONTROL PORT OF SAID CYLINDER OF THE TIME-DELAY DEVICE AND SAID OUTLET CHAMBER, A FIFTH DUCT CONNECTED BETWEEN THE OUTLET PORT OF SAID CYLINDER OF THE TIME DELAY DEVICE AND SAID THIRD PORT, A THIRD FLUID-ACTUATED DEVICE COMPRISING A THIRD CYLINDER HAVING IN SIDE WALLS THEREOF A FIFTH PORT IN FLUID FLOW COMMUNICATION WITH SAID INLET CHAMBER, A SIXTH PORT IN FLUID FLOW COMMUNICATION WITH SAID OUTLET CHAMBER, AND SEVENTH AND EIGHT PORTS IN FLUID FLOW COMMUNICATION WITH SAID FOURTH PORT, A SPOOL VALVE MOVABLE IN SAID THIRD CYLINDER BETWEEN A FIRST POSITION IN WHICH IT DEFINES A FLOW PATH BETWEEN SAID FIFTH AND SEVENTH PORTS ARE A SECOND POSITION IN WHICH IT DEFINES A FLOW PATH BETWEEN SAID SIXTH AND EIGHT PORTS, AND DUCTING CONNECTING SAID CONTROL VALVE TO SAID EXHAUSTVALVE ACTUATOR, SAID CONTROL VALVE BEING OPERABLE TO SUPPLY FLUID TO SAID EXHAUST-VALVE ACTUATOR TO OPEN SAID OUTLET PORT THEREBY TO CREATE A PRESSURE DIFFERENCE ACROSS SAID FIRST PISTON TO OPEN SAID FIRST PAIR OF SWITCH CONTACTS, AND CREATE A PRESSURE DIFFERENCE ACROSS SAID SECOND PISTON, TO OPEN SAID SECOND PAIR OF SWITCH CONTACTS AFTER A TIME DELAY DETERMINED BY SAID TIME-DELAY DEVICE. 